1. Field of the Invention
This invention relates generally to electrical distribution systems and in particular to distribution systems for direct current electrical power.
2. Background of the Prior Art
High-density computer environments utilizing alternating current (AC) power supply blade server technology are presenting major challenges to owners and operators. Typical facility infrastructures cannot accommodate the added heat loads and reliability requirements of such high-density installations.
Critical components, such as computers, etc., require a highly reliable source of electric power and can generally tolerate only slight differences from standard 120 VAC, 60 Hz power that is then protected by an uninterruptible power supply (UPS). A UPS generally protects a computer against four different power problems:                Voltage surges and spikes—Times when the voltage on the line is greater than it should be.        Voltage sags—Times when the voltage on the line is less than it should be.        Total power failure—Times when a line goes down or a fuse blows somewhere on the grid or in the building.        Frequency differences—Times when the power is oscillating at something other than 60 Hertz.        
Recent studies by various organizations and manufacturers have lead to the joint philosophy that more cost effective, more reliable, more maintainable, and more simplified electrical power distribution systems are needed for critical environments. With this in mind, it has been found that typical designs for critical environments utilize similar high cost equipment to provide reliability to critical power environments. All systems utilize components to convert utility provided, alternating current (AC) power to direct current (DC) power for an energy storage interface, such as batteries, back to AC power for plant floor distribution, and then back to DC power for internal equipment utilization. FIGS. 1-3 illustrate typical critical power distribution systems for facilities of different sizes.